Moistureproof material and method of making same



Patented Nov, 17, 1936 1 moisrtmarxoo .MAKING 2,061,374 MATERIAL AND METHOD SAME - g William Hale Charcli, Buffalo, N. Y., assignor, by

mesne assignments, to E; I. du Pont de Nemours' & Company, Wilmington,

ration of Delaware No Drawing.s

25 Claims.

. This invention relates to mostureproo'f materials and to a method of preparing the same. -More particularly, it relates to preparing moisture proof materials with a wax composition 5 which results in a product having a non-tacky surface which does not appreciably smear on handling. a

In copendi'ng application Serial No.

341,834, filed February 21', 1929, now Patent 1,989,681, there is disclosed a processof preparing moistureprooi sheets or films of regenerated cellulose. According to one embodiment of that process, 'a sheet or film of regenerated cellulose, while in the gel state, is impregnated with a dispersion containinga wax and a plasticizer.

I'he impregnated material is then passed through the drying rolls of the usual casting machine whereby the material is dried. The product'resulting from such a procedure possesses an unde-* sirable greasy surface and doesnot possess the necessary non-tacky surface. To overcome this, the aforementioned invention contemplates applying a surface coating which poss the I desirable surface characteristics.

I have found that-'1' can prepare a moistureprooi material having the desirable non-tacky surface, and which does not appreciably smear on handling, by treating a base formed of a nonfibrous, non-foraminous and preferably transparent material, for example, a cellulose mate-- rial such as regenerated cellulose, cellulosic de-' rivatives, for example, cellulose ethers, cellulose acetate, cellulose nitrate, etc., or an albuminous materiaksuch as gelatin,,agar-agar, hardened or not as desired, with an aqueous dispersioncontaining a moisture-proofing ingredient, such as a wax and a hardening agent, which may be a wax, for themoistureproofing wax and subjecting the treated base to a temperature at least 40 approximately equal to the meltingpoint ofthe moistureproofing wax ingredient, preferably simultaneously with or alternately "subsequent to the drying ofthe treated base.

It is therefore an object of this invention to 45 provide a transparent moistureprooi material consisting of a base formed of a non-fibrous, nonforaminous and preferably transparent material, for example, a cellulosic materiah such as regenerated cellulose, cellulose derivatives, or an 50 albuminous'material, substantially coated with a moistureproofing wax composition and preferably containing a hardening agent for the wax, said material having a non-tacky surface which does not appreciably smear on handling.

q amoistureproof materialby treating a base preferably transparent material, for example, a cellulosic material such as regenerated cellulose, 60 cellulose derivatives or an albuminous substance,

Another object of this invention is to provide formed of a 'nonfibr'o'us, non-foraminous andsion' containing a moistureproofing ,wax, a hard- Del., a corpo- Application January 9, 1932, erlal No. steam with an equeous dispersion containing-"a moistureproofing wax and a hardening agent for said moistureproofing wax, and subjecting the treated material to a temperature at least approximatelyequal to the melting point of. the wax, either preferably simultaneous with or alternately subsequent .to the drying thereof.

A specific object of this invention is to provide a method which may be used in combination with the usual procedure for manufacturing sheets or films of regenerated cellulose, and which comprises treating -a desulphured and bleached sheet or film of regenerated cellulose while inthe wet state with an aqueous disperening agent for said wax and preferably also a softening agent for .the regenerated cellulose,

' prior to thedrying of the-film, and thereafter drying the treated film in such a manner that preferably the treated film is first dried and then subjected to a temperature at least approximately equal to the melting point of the wax in the composition and finally to a temperature less than the melting point of the max in the composition. v

Other objects will become apparent from the following description and appended claims.

In accordance with one illustrative embodiment of the invention, a sheet or film oi. regenerit is dried. It

' passed through a through squeeze rolls tal, wherein the film ated tfiallulose cast in the usual manner and washed, desulphured and bleached, as is well mown in the art, prior to drying and while in the wet gel state is conducted into abath containing an aqueous dispersion comp a moistureproofing wax, a hardening agent for the moistureproofingwax and preferably w a softener i'orthe regenerated cellulose. The film is then treated as hereafter more fully described.

In one illustrative embodiment, the treated film, after it leaves the bath and the excess composition removed in any convenient manner, may be fed through a series of drier rolls until may then be passed through a short series of drier rolls maintained at a temperature above the melting point 0! the wax in the mixture. Finally. the treated film may be a series of rolls maintained at less than the melting point of The .film, after it has been to cool, is wound into a roh may be slit a temperature the wax mixture. cooled or permitted and shipped. If desired, the film and wound into smaller rolls or cut into sheets. In another exemplification of the invention, the film, as itleaves the bath; may be conduc and then through a straight tunnel drier, either vertical or horizonis'heatedby warm air until the film and coating arecompletely dried and the waxes have been melted and coalesced to iorm transparent coatings. Subsequently. the oo the major portion of the water is removed, and 1 then passed through a tunnel drier as above described wherein the coated film is substantially completely dried and subjected to a temperature at least equal to the melting or crystallization. point of the waxes in the compositions.

Still another modification contemplatesdrying the film, after the excess composition has been removed, by passing the same over rolls main-.

tained at a temperature below the melting or crystallization point of the waxes, and then heating the dried coated film at a temperature above the melting or crystallization point of the waxes in a tunnel, as above described. The film is then cooled and wound into .rolls, slit or cut into sheets, as desired.

In each of the modifications described, if, after the treatment in the tunnel, the coated film is to be passed'over rolls, it is advantageous to permit.

the film to cool to a temperture at least sumcient to allow solidification of the waxes prior to contacting with the rolls.

Instead of heating the coated film in a tunnel as above described, it may be heated by hot plates orradiating fins disposed on both sides of the filmand at a short distance therefrom. Due to the high heat, the waxes will be melted rather quickly. The time of passage of the film through these heating elements should therefore be of such duration that the film itself does not lose any appreciable amount of its hygroscopic moisture which would cause embrittlement. In this procedure, the film, after passing through the heating elements, should be chilled quickly.

The aqueous dispersion referred to above comprises one or more moistureproofing waxes or waxy substances and an agent for hardening the moistureproofing ingredients, whereby the coated base will be provided with anon-tacky surface which does not appreciably smear on handling. In the case where the process is combined with the process of preparing sheets or films of regenerated cellulose, the aqueous bath may also contain a softener for the regenerated cellulose.

Paramn wax is the preferred moistureproofing I A's illustrative of the hardening agents for the I moistureproofing waxes which can be used may be mentioned the hard waxes, such as candelilla wax, carnauba wax and some of the synthetic waxes; or resins, either natural or synthetic, for example, gum mastic, gum dammar, zinc resinate, coumarin resins, glyptal resins and toluene sulphonamide formaldehyde condensation products.

Any suitable dispersing agent, of which ammonium stearate, triethanolamine stearate, p tassium abietate and sulphonated oils are illustrative examples, may be employed.

When the composition is to be employed with sheets or films of regenerated cellulose, any suitable softener for regenerated cellulose, such as glycerin, may be incorporated in the dispersion.

The proportions of the ingredients mayvary within wide limits, depending inter alia on the degree of moistureproofness, the character of the surface, and the transparency of the product, A dispersion in which the solid ingredients are present in quantities from 2%-20% by weight has been'found to'give excellent results. When used to treat sheets or films of regenerated cellulose, the dispersion may also contain glycerin or some other softener in an amount from 2%-15% by weight.

In order to more clearly explain the invention and particularly the composition of the baths,

the following specific illustrative embodiments are set forth:

' Parts (1) Candelilla wax 60 Paramn wax (M. P. 60 C.) 28 Ammonium stearate 12 This composition is prepared by melting the candelilla wax, the paraffin wax and stearic acid together. The. molten wax. mixture is poured into agitated water containing ammonium hydroxide which has been heated to a temperature of about 95 C. The stirring is continued until the emulsion so produced decreases in temperature to about 50 C.

The quantities of ammonium hydroxide and wax used.

To employ this emulsion with sheets or films of regenerated cellulose it is diluted with water containing glycerin to yield a system containing approximately 10% of solids and of glycerin by weight.

In the foregoing example, the dispersing agent is a soap preferably produced in situ by the reactionof the alkali and fatty acid. When other dispersing agents, such as sulphonated oils, are

employed'the procedure must be somewhat m0di-. fied. Thus,.when sulphonated oils constitute the dispersing agent, these are first dissolved in water, preferably heated, and the molten wax mixture added to the heated solution with agitation.

' Parts (2) Candelilla wax 60 High melting parailln-.. 24 Gum mastic--. 4 Triethanolamine stearate 12 Parts (3) Carnauba wax 50 Chlorinated diphenyl 20 High melting paraflin 20 Potassium abietate Parts (4) Candelilla wax 50 Chlorinated diphenyl Spermaoeti 20 Potassium abietate 10 Parts (5) Candelilla wax 60 I-Iigh'melting paraflln 24 Zinc resina 6 Ammonium stearate 10 The compositions set forth in Examples 2-5 inelusive are prepared in a manner similar to that set forth under Example 1. To produce the final bath for the treatment of sheets or films of regenerated cellulose, each -of the above compositions is mixed with water containing glycerin to yield a system containing 2%-20% of solid ingredients and 2%-15% of glycerin and preferably 10% of solids and 5% of glycerin.

It is apparent that if desiredthe glycerin may tureproofed in accordance with the principles of this invention. In such a case, the dried sheet or film of regenerated cellulose may, if desired, be first wetted with water, though this is not essential, and then treated as above described.

As apparent from the foregoing description, the invention is also not restricted to the treatment of sheets or films of regenerated cellulose. It is equally applicable to other non-fibrous, non-- 'foraminous and preferably transparent cellulosic materials, such as sheets or films of cellulose derivatives, for example; cellulose ethers, cellulose nitrate and cellulose acetate; sheets or films of albuminous substances, such as the preferred hardened gelatin, agar-agar, ,and the like; sheets or films of regenerated cellulose coated with non-moistureproofing compositions, such as pyroxylin lacquers, wi'nishes, shellac, and the like.

When the dispersions hereinbefore described are to be used to treat films made of or materials coated with nitrocellulose, cellulose acetate, shellac etc., the glycerin may be omitted and there may be incorporated in the continuous phase of the dispersion a water-soluble organic liquid, such as ethyl alcohol, wood alcohol, esters of ethylene glycol etc., which serve to improve the spreading or wetting power ofthe dispersion whenapplied to materials of thetype mentioned. Such dispersions may be prepared by dissolving the waxes or wax mixture in asolvent, such as toluene, benzene or the like and then emulsifying this solution in water containing the watersoluble organic liquid. Alternatively, these dispersions may be prepared as set forth in examples l-5 inclusive, with the modification that the aqueous medium contains the water-soluble organic liquid. v

The material constituting another part of this invention, as evident from the foregoing, consists of a base preferably formed of a non-fibrous,

'non-foraminous and preferably transparent cellulosic material, such as regenerated cellulose, cellulose derivatives or other substances, for ex-' ample, alhuminous substances or the like, coated with a moistureproofing wax composition, preferably containing an agent which functionsas a hardening agent for the moisture-proofing com-' position and aids in imparting to the product a non-tacky surface which does not/appreciably smear on handling. The material resists the penetration of moisture or water vapor. therethrough to an extent at least 10 times, and in many cases 20, 30, 40, 50 or moretimes, as effective as the uncoated sheet when tested in accordance with the test set forth in .the Journal be joined or sealed to of Industrial and Engineering Chemistry on page 575, vol. 21, No.6-(June 1929). It'is also-flexible and capable of being bent and folded withoutsubstantially losing its effectiveness.

when the base is transparent, the final product is also transparent, the degree of transparency of the final product being at least approximately equal to that of the base before treatment. Because'of the fact that the impregnating-medium consists essentially of wax, the material may itself, similar or non-similar materials, by heat-sealing.- This feature is extremely desirable when the material is employed as a wrapping tissue.

Since it is obvious that various changes and modifications may be made inthe above descripformed of a non-fibrous cellulosic material with an aqueous dispersion containing a moistureproofing wax and a-hardening agent for said wax I in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky "surface which does not appreciably smear on handling, and subjecting the-treated material to a temperature at least approximately equal to the melting point of the wax in the composition. 2. A method of preparing a transparent moistureproof material having a ncn-tacky surface which does not appreciably smear on handling which consists in treating a transparent base formed of a non-fibrous cellulosic material with an aqueous dispersion containing a moistureproofing waxand a hardening agent for said wax in proportions .to, produce, upon heating 'to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureprooi product having a non-tacky surface which does not appreciably smear on handling, drying the treated material, and subjecting the dried material to a temperature at least approximately equal to..the melting point of the wax in the composition.

3:--'A method of preparing a transparent moistureproof material having a non-tacky surface which does not appreciably smear orr handling which consists in treating a transparent base formed of regenerated cellulose with an. aqueous dispersion containing-a molstureproofing wax and a hardening agent for-said wax in proportions to produce, upon heati'ngto a temperature at least approximately equal to the-melting point of the wax in the composition, a transparent mois ,tureproof product having a non-tacky surface which does not appreciably smear on handling, and subjecting the treated material to a temperamm at least approximately equal to the melting point of the wax in the composition.

4. A methodof preparing a transparent moistureprooi material having a' non-tacky surface.

whichdoes not appreciably smear on handling which consists in treating a transparent base formed. of regenerated cellulose with an aqueous dispersion containing a moistureproofing wax and a hardening agent "for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax.in the composition, a transparent moistureproof product having a non-tacky surface which does'n'ot appreciably smear on handling, drying the treated material, and subjecting the dried material to a' temperature at least approximately equal to the melting point of the wax in the composition.

5. A method of preparing a transparent moistureproof material having a non-tacky surface which does not appreciably smear on handling which consists in treating a transparent base formed of a cellulosederivative with an aqueous dispersion containing a moistureproofing wax and a hardening agent for said wax in proportions to produce, uponheating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling,

and subjecting the treated material to a temperature at least approximately equal to the melting point of the wax in the composition.

6. A method of preparing a transparent moistureproof material having a non-tackysurface which does not appreciably smear on handling which consists in treating a transparent base formed of a cellulose derivative with an aqueous dispersion containing a moistureprooiing wax and a hardening agent for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, drying the treated material, and subjecting the dried material to a temperature at least approximately equal to the meltingpoint of the wax in the composition.

'7. A method of preparing a; transparent moistureproof material having a non-tacky surface which does not appreciably smear on handling least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, and subjecting the treated material to a temperature at least approximately equal tothe melting pointof the wax in the composition.

8. A method of preparing a transparent moistureproof material having a non-tacky surface which does, not appreciably smear on handling dling, drying the treated material, and subjecting the dried material to a temperature at least approximately equal to the melting point of the wax in the composition.

9..A method of preparing transparent moistureproof films of regenerated cellulose which consists in treating a transparent sheet or film of regenerated cellulose with an-aqueous dispersion,

containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately tureproof films of regenerated cellulose which consists in treating a transparent sheet or film of regenerated cellulose with an aqueous dispersion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the com-' position, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, drying the treated material, and subjecting the dried material to a temperature at least approximately equal to the melting point of the wax in the composition.

11. A method of preparing transparent moistureproof films of regenerated cellulose which consists in treating a transparent sheet or film of regenerated cellulose with an aqueous dispersion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, subjecting the treated-material to a temperature at least approximately equal to the melting point of the wax in the composition, and then subjecting the material to a temperature less than the melting point of the wax in the composition.

12. A method of preparing transparent moistureproof films of regenerated cellulose which consists in treatinga transparent sheet or film of regenerated cellulose with an aqueous dispersion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smearon handling, drying the treated material, subjecting the dried material to a temperature at least approximately equal to the melting pointofthe wax in the composition, and

then subjecting the material to a temperature less than the melting point of the wax in the composition. L, A i, 1

13. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on' handling and which consists in casting a cellulosic solution, purifying the cast. film, treating the desulphured and bleached film while in the wet gel state with an aqueous dispersion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, and

subjecting the treated film to a temperature at least approximately equal to the melting point of the wax in the composition.

14. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in casting a cellulosic solution, purifying the cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous dispersion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximatelyequal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, drying the treated film,'and subjecting the dried film to a temperature at least approximately equal to the melting point of the wax in the composition.

15. A process of preparing a transparent mois-' tureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in castin a cellulosic solution, purifying the cast film, treating the desulphured' and bleached film while in the wet gel state with an aqueous dis-v persion containing a moistureproofing wax, a hardening agent for said wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which does not appreciably smear on handling, subjecting the treated film to a temperature at least approximately equal to the melting point of the wax iipthe composition, and then subjecting the material to a temperature less than the melting point. of the wax in the composition.

16. (A process of preparing atransparent mois tureproof pellicle of regenerated cellulose having a non-tacky surface which does not apprci= ably smear on handlingand which consists, in casting a cellulosic solution, purifying the cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous dis.- persion containing a moistureproofing 'wax, a

hardening agent for said'wax and a softener for the regenerated cellulose in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproofproduct having a non-tacky surface which does not appreciably smear on handling, drying the treated film, subjecting the dried film to a temperature at least approximately equal to the melting point of the wax in the composition, and then subjecting the material to a temperature less than the melting point of the wax in the composition.

17. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in castings; cellulosic solution, purifying the cast film, treating the desulphured and bleached film while in the wet gel "state with an aqueous dispersion containing a moistureproofing wax and a hardening agent for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting pointof the" wax in the composition,

a transparent moistureproof product having a non-tacky surface which the does not appreciably smear on handlingfand subjecting the treated film to a temperature ,at least approximately equal to the melting point of. the wax in the composition.

18. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in casting a cellulosic solution, purifying the cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous dispersion containing a moistureproofing waxand a hardening agent for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of' the wax in the composition, a transparent moistureproof product having a non-tacky surface which doesnot appreciably smear'on handling, drying the treated film, and subjecting the dried film to a temperature at least approximately equal to the melting point of the wax in the composition.

19. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in casting a cellulosic solution, purifying the cast film,

treating the desulphured and bleached film whilejecting the treated film to a temperature at least approximately equal to the melting point of the wax in the composition, and then subjecting the material to a temperature less than the melting point of the wax in the composition.

20. A process of preparing a transparent moistureproof pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which consists in casting a cellulosic solution, purifying the cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous dispersion containing a moisturepr'ooflng wax and a hardening agent for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which doesfnot appreciably smear on handling, drying treated film, subjecting the dried film to a temperature at least approximately equalto the melting point of the wax in the compositiomand then subjecting the material to a temperature less than the melting point of the wax in the composition. i 1 v v 21. A "method of preparing a transparent moistureproof material having a non-tacky surface which does not appreciably smear on handling which consists in treating a transparent base formed of a non-fibrous material with an aqueous dispersion containing a moistureproofing wax and a hardening agent for said wax in proportions to produce, upon heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof product having a non-tacky surface which 22. A method of preparing. a transparent moistureproof material having a non-tacky surface which does not appreciably smear on handling which consists intreating a transparent base formed of a non-fibrous material with an aqueous dispersion containing a moistureproofing wax and a hardening agent for said wax in proportions to.

. tureproof'pellicle of regenerated cellulose having a non-tacky surface which does not appreciably smear on handling and which'consists in casting a cellulosic solution, purifyingthe cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous emulsion comprising 2% to of solid ingredients 'comprising 60 parts of candelilla wax, 28 parts of high melting paraifin wax and 12 parts of ammonium stearate, the proportions being byweight to produce, upon heating to a temperature at least approximatelyequal to the melting point of the wax in the composition, a transparent moistureproof regenerated cellulose pellicle having a non-tacky'suri'ace which does not appreciably smear on handling, drying the treated film,

and subjecting the dried film to a temperature at least approximately equal to the melting point of the wax in the composition. I

24. A process of preparing a transparent mois tureproof pellicle of regenerated cellulose havlnga non-tackysurface which does not appreciably smear on handling and which consists in casting a cellulosicsolution, purifying the cast film, treating the desulphured and bleached film while in the wet gel state with an aqueous solution comprising 2% to 20% of solid ingredients comprising 60 parts of candelilla wax, 24 parts of high melting paramn wax, (parts of gum mastic and 12 parts of triethanolamine stearate, the proportions being by weight to produce, upon .heating to a temperature at least approximately equal to the melting point of the wax in the composition, a transparent moistureproof regenerated cellulose pellicle having a non-tacky surface which does not appreciably smear on handling,

drying the treated film, and subjecting the dried film to a temperature at least approximately equal to the melting point of the wax in the composition.

25. A process of preparing a transparent moistureproof pellicle of regenerated cellulo'se having a non-tacky surface which does not appreciably smear on handling and which consists in casting a cellulosic solution, purifying the cast film,

treating the desulphured and bleached film while I in the wet gel state with an aqueous solution comprising 2% to 20% of solid ingredients comprising 60 parts of candelilla wax, 24 parts of 

